Shunt trip and under voltage device



March 23, 1965 F. E. MYERS 3,175,064

SHUNT TRIP AND UNDER VOLTAGE DEVICE Filed April 5, 1962 6 Sheets-Sheet 1 INVENTOR. FEL/X MMEAS BY fldrledl. 5/01. 595519, 9:: a f JbFF'lY March 23, 1965 F. E. MYERS SHUNT TRIP AND UNDER VOLTAGE DEVICE 6 Sheets-Sheet 2 Filed April 5, 1962 INVENTOR. FEL/X E- NYE 9'6 March 23, 1965 F. E. MYERS SHUNT TRIP AND UNDER VOLTAGE DEVICE 6 Sheets-Sheet 3 Filed April 5, 1962 March 23, 1965 F. E. MYERS SHUNT TRIP AND UNDER VOLTAGE DEVICE 6 Sheets-Sheet 4 Filed April 5, 1962 INVENTOR. FL /X E. MIKE/9.)

March 23, 1965 F. E. MYERS 3,175,064

SHUNT TRIP AND UNDER VOLTAGE DEVICE Filed April 5, 1962 6 Sheets-Sheet 5 INVENTOR. FEA/X E. My'eJ' BY Oszemewxykaza, $548 arms/Y F E. MYERS SHUNT TRIP AND UNDER VOLTAGE DEVICE March 23, 1965 6 Sheets-Sheet 6 Filed April 5, 1962 Qb m l w INVENTOR. PEA/x E. MYi/QJ' United States Patent ration of Pennsylvania Filed Apr. 5, 1962, Ser. No. 185,328 7 Claims. (Cl. 200106) The instant invention relates to auxiliary trip units for circuit breakers and more particularly to a shunt trip or under voltage trip unit that may be added to a standard multi-phase molded case circuit breaker without costly or special mechanism changes In a conventional multi-phase molded case circuit breaker the occurrence of a fault in any of the phases will be effective to bring about simultaneous opening of all phases. Typically, a single contact operating mechanism is provided for all phases and an individual fault rcsponsive means is provided for each phase. All of the fault responsive means are effective to operate a common tripper bar whose operation causes the operating mechanism to simultaneously open the contacts of all phases.

It is often desirable to bring about opening of the circuit breaker under other than the existence of over current fault conditions. For example, if there is an under voltage condition existing, fault currents may not be generated, yet equipment may not be operating in its intended manner. Under these circumstances it may be best that operation of the equipment be halted. This is accomplished by providing an auxiliary tripping means, otherwise known as an under voltage trip unit.

Briefly, the under voltage trip unit of this invention includes an electro-magnet having an armature biased away from the magnet. Also provided is a latch member which is biased toward a position in which the latch member will engage the circuit breaker common tripper bar for operation thereof to automatically trip the circuit breaker. A pin means carried by the armature is provided to maintain the latch member remote from the tripper bar when the armature is attracted to the magnet.

The armature will remain attracted to the magnet so long as the voltage applied to the circuit breaker does not fall below a predetermined value. When the voltage falls below the predetermined value the force of the magnet is no longer effective to overcome the force of the armature biasing means so that the pin means is moved to release the latch member whose biasing means is then effective to move the latch for operation of the trip bar.

When the circuit breaker contacts move to open circuit position a relatching blade carried by one of the movable eontact arms engages the latch member and operates the latch member to a position where it will be engaged by the pin means when the armature is again attracted to the magnet.

With a slight modification, that is, merely moving the pin means, the under voltage device is readily transformed into a shunt trip device. Under these circumstances, the pin means will maintain the latch member remote from the tripper bar when the armature is remote from the magnet. Upon movement of the armature to the magnet the pin means will release the latch member for movement thereof into engagement with the tripper bar.

Accordingly, a primary object of the instant invention is to provide a novel construction for an auxiliary trip device which does not require costly or special mechanism changes in an existing circuit breaker.

Another object is to provide an auxiliary tri device which may readily be utilizedfor either shunt trip or under voltage trip.

Still another object is to provide an auxiliary trip device which includes a latch member biased to a position for operating a common tripper bar.

These as well as other objects of the instant invention shall become readily apparent after reading the following description of the accompanying drawings, in which:

FIGURE 1 is a perspective of a molded case circuit breaker, with the cover removed, which includes an under voltage trip device and a shunt trip device constructed in accordance with the teachings of the instant invention.

FIGURE 2 is a plan view of the circuit breaker of FIG- URE 1 with the cover removed.

FIGURE 3 is a cross-section taken through line 3-3 of FIGURE 2 looking in the direction of arrows 33.

FIGURE 4 is an end view of the under voltage trip device.

FIGURE 5 is a side elevation of the under voltage trip device shown with the magnet energized and the circuit breaker contacts open.

FIGURES 6A-6C are somewhat schematic side elevations of the under voltage trip device illustrating the elements in their various operating positions. In FIGURE 6A the armature is in engagement with the magnet and the circuit breaker contacts are open. In FIGURE 6B the magnet is energized and the circuit breaker contacts are closed with the trip unit latch member being maintained against operation of the tripper bar. In FIGURE 6C the contacts are still closed but the tripper bar has been operated to release the contact operating mechanism.

FIGURES 7A-7C are side elevations in schematic form of the shunt trip device. In FIGURE 7A the armature is remote from the magnet and the circuit breaker contacts are open. In FIGURE 73 the circuit breaker contacts are closed, the armature is remote from the magnet and the latch member is maintained against operation of the tripper bar. In FIGURE 7C the circuit breaker contacts are closed, the armature is in engagement with the magnet and the latch member has rotated the tripper bar.

Now referring to the figures. Molded case circuit breaker 20 comprises a housing including base 21 and removable cover 22. Base 21 is divided into three longitudinal compartments by partitions, 23 and 24, with each compartment containing substantially identical current carrying elements and fault sensing elements. In addition the center compartment contains contact operating mechanism 25 whose operation is efiective to simultaneously move the contact arms 27 of all three phases. Contact operating mechanism 25 is described in copending application Serial No. 108,812 filed May 9, 1961 with E. Wortmann as inventor, entitled U-Shaped Cradle for Circuit Breaker, and assigned to the assignee of the instant invention. Fault sensing means 26 is described in copending application Serial No. 117,464, filed June 15, 1961, now Patent No. 3,125,651, with I. Brumfield as inventor, entitled Magnetic Trip Means, and assigned to the assignee of the instant invention.

The current path through each phase of circuit breaker 20 comprises terminal strip 28, bimetal heater 29, strap 30, flexible braid 31, movable contact arm 27, movable contact 32, stationary contact 33, and terminal strip 34.

of FIGURE 3 in order for contact arm 27 to be in the' closed position shown. Cradle is maintained in latched position by having its latch tip 36 engaged by auxiliary latch means 37 which in turn is maintained in position by main latch 38 carried by common tripper bar 39. As is well known to the circuit breaker art, common tripper bar 39 extends across all three phases so as to be operable by the time delay tripping means bimetal 41 as well as the instantaneous trip means armature 42 of all phases. Tripping occurs when tripper bar 39 is rotated sufiiciently clockwise from its position of FIGURE 3 to free auxiliary latch means 37 from main latch 38.

As will be more fully explained hereinafter, under voltage trip device 45 (FIGS. 4-6C) is provided for antomatically opening the breaker when the line voltage drops below a. predetermined value and a shunt trip device (FIGS. 7A-7C) is provided for automatic tripping of breaker 20 from a remote location or as a result of the occurrence of a predetermined condition not necessarily an electric overload.

Now referring more particularly to FIGURES 4 through 6C. These figures illustrate under voltage trip device 45 which comprises an electro-magnet consisting of generally U-shaped laminated core 51 having coil 52 mounted to one leg thereof. Leads 53, 54 for coil 52 extend through apertures 55 in the bottom of base 21 and are generally connected across two phases of breaker 20 on the line side thereof. A plurality of rivets 56 extend through the laminates of core 51 and secure side plates 57 to core 51.

Rivets 58 extend through the laminates forming armature 60 and secure armature side plates 59 to armature 60. Pin 61 extends through elongated apertures 62 in side plates 57 as well as through apertures in side plates 59 to pivotally mount armature 60 to core 51. Screw means 63 secures angle bracket 65 to leg 64 of the bracket which furnishes bearing support for tripper bar 39. Screw means 66 secures bracket 65 to one of the magnet side brackets 57. Screw means 67 extends through bracket 64 into base 21 to secure under voltage trip unit 45 in operative position on base 21.

Biasing means urging armature 60 away from magnet 51 is provided by two coil springs 68, 68. Each of the springs 68 is fixed at one of its ends to a magnet side bracket 57 and at the other end to an adjusting screw 69. Screw 69 extends through an aperture in an outturned portion of armature side bracket 59 with spring 63 disposed on one side of this out-turned portion and nut 76 threadably mounted to screw 69 on the other side of this out-turned portion.

Downward extensions of magnet side brackets 57 are provided with aligned apertures which form bearings for pin 71 which constitutes a pivot for latch member 72. Torsion spring 73 mounted to pin 71 biases latch member 72 in a counterclockwise direction with respect to FIGURE 5. Latch member 72 includes latching tip 74 on one side of pivot 71 and trip extension 75 on the other side of pivot 71. Further, latching member 72 includes downward extension 76 which is engaged by relatching plate 77, carried by contact arm 27, when the circuit breaker contacts are open. Trip extension 75 is engageable with clip 78, mounted to tripper bar 39, when latching member 72 is inits most counterclockwise position.

The rear extensions of armature side plates 59 are provided with a first set of aligned apertures between which latching pin 79 extends, a second set of aligned apertures through which resetting pin 86 extends, and a third set of aligned apertures 81. In the case of an under voltage triping as a shunt trip device 50 apertures 81 will be occupied Upon the occurrence of an under voltage condition the by a pin.

With circuit breaker contacts 32, 33 in the engaged position (FIG. 3) and with sufficient voltage being applied to coil 52, the elements of under voltage trip unit 45 are in the positions of FIGURE 613. That is, armature 60 is attracted to magnet 51, against the force exerted by biasing springs 68, and biasing spring 73 has moved surface 74a against latching pin 79. It is noted that for this position of latch member 72 tripper bar 39 remains in its most counterclockwise position being urged there by spring 39a. It is also to be noted that there is an extensive space between latch member extension 76 and relatching plate 77.

Upon the occurrence of an under voltage condition the force of the armature biasing spring 68 is sufficient to overcome the magnetic force generated by magnet 51 so that armature 60 is moved counterclockwise about its pivot 61 to the position of FIGURE 60. This moves latching pin 79 to the right of latching surface 74a thereby releasing latch member 72. Torsion spring 73 then drives latch member 72 to the position of FIGURE 6C where trip extension 75 engages tripper bar clip 78 thereby rotating tripper bar 39 clockwise and bringing about opening of circuit breaker 20.

As contact arm 27 moves to open circuit position, relatching plate 77 engages extension 76 driving latching member 72 clockwise about its pivot 71 with surface 74b engaging resetting pin 80. This drives armature 60 clockwise about its pivot 61 to the position of FIGURE 6A. If, when circuit breaker 20 is next operated to closed circuit position, there is suflicient energization for coil 52 then armature 60 will remain in the position of FIGURE 6A and latching surface 74a will engage latch pin 79. If there is insufficient energization for coil 52 when the next closing operation takes place for circuit breaker 20, then 'as contact arm 27 begins to move to closed circuit position latching member 72 will move counterclockwise about its pivot '71 and surface 74b will move downward. This in turn will enable armature 66 to move counterclockwise about its pivot 61 so that latching pin 79 will move clear of surface 74a and latching member 72 will be effective to cause clockwise rotation of tripper bar 39 to bring about tripping of circuit breaker 20.

Shunt trip device 50 is substantially identical in construction to under voltage tripping device 45. The main difference being that the latching and resetting pins 79, 80 have been replaced by a single pin 91 which extends through armature side plate apertures 81. It is noted that the brackets for mounting shunt trip device 50 to base 21 are mirror images of the brackets which perform similar functions for under voltage tripping device 45.

Operation of shunt trip device 50 is as follows. With the circuit breaker contacts 32, 33 in closed position, armature 60 is maintained spaced from magnet 51 since coil 52 is deenergized. Spring 73 biases latching member 72 counterclockwise about its pivot 71 so that surface 74c is in engagement with pin 91 (FIGURE 7B).

When coil 52 is energized, armature 60 is moved clockwise about its pivot 61 thereby moving pin 91 to the left of surface 740 so that spring 73 is free to drive latching member 72 counterclockwise about its pivot 71 to the solid line position of FIGURE 7C. In this position trip extension 75 is in engagement with tripper bar clip 92 rotating the latter clockwise to bring about opening of the circuit breaker.

As contact arm 27 moves toward open circuit position relatching plate 77 engages extension '76 to drive latching member 72 clockwise about its pivot 71. During this movement surface 74b engages pin 91 driving armature 60 clockwise against the force of biasing springs 68 until the lower end of surface 74b is above pin 91. Thereafter, armature 66 is free to move counterclockwise to the position of FIGURE 7A.

It is noted that the purpose of the elongated slots in magnet side plates 57 prevents over-latching of armature 60 on the under voltage device 45 where undue stresses would otherwise be put on the unit. The elongated slots take care of any overtravel of contact arm 27 or mis-adjustment of relatching plate 77. The armature 60 and pin 61 are allowed to move vertically in the elongated slots 62 of magnet side plates 57 against the bias of the springs 68, which also act as a cushion. Further, the same effect is obtainable by having pivot 61 carried by magnet side plates 57 and providing armature side plates 59 with elongated apertures 52.

In prior art devices, it was necessary to include an additional leaf spring acting on the armature to cushion re latch shock or overtravel. Springs 68 of this invention serve the dual function of armature return and relatch cushion. In addition, springs 68 maintain armature pin 61 in the bottom of the elongated slots for normal operation.

It is also noted that relatch plate 77 is of a spring clip ty e with the ends thereof being compressed between the crossbar which mounts contact arms 27 and the protrusion to which the contact pressure spring is anchored. The center leaf of the relatch plate 77 is resilient so as to correct for relatch mis-adjustment.

Although preferred embodiments of this novel invention are described herein, many variations and modifications will now be apparent to those skilled in the art and, therefore, it is preferred that this invention be limited not by the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A auxiliary trip unit for a circuit breaker, said unit comprising an electro-magnet, an armature, including an extending portion, biased away from said electro-magnet to a first position, energization of said electro-magnet being effective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position for operation of a circuit breaker automatic tripping means, said member being mounted for movement away from said tripping position to a latching position, means for engaging said member and maintaining same in said latching position, said means being carried by said extending portion of said armature for operation in accordance with movement of said armature.

2. An auxiliary trip unit for a circuit breaker, said unit comprising an electro-magnet, an armature biased away from said electro-magnet to a first position, energization of said electro-magnet being efiective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position for operation of a circuit breaker automatic tripping means, said member being mounted for movement away from said tripping position to a latching position, means for engaging said member and maintaining same in said latching position, said means being operatively connected to said armature for operation in accordance with movement of said armature, said means includes latching means alternately positionable to release the member when the armature is in the second position or to release the member when the armature is in the first position, whereby said trip unit may be connected between shunt trip and under voltage operation.

3. An auxiliary trip unit for a circuit breaker, said unit comprising an electro-magnet, an armature biased away from said electro-magnet to a first position, energization of said electro-magnet being effective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position for operation of a circuit breaker automatic tripping means, said member being mounted for movement away from said tripping position to a latching position, means for engaging said member and maintaining same in said latching position, said means being operatively connected to said armature for operation in accordance with movement of said armature, said means comprises a first latching portion and a second reset portion, said first latching portion positioned to release the latching position of said latch member when the armature is in the first position, said second reset portion being engaged by said member for movement of the armature to the second position by movement of the member to said latching position.

4. An auxiliary trip unit for a circuit breaker, said unit comprising an electro-rnagnet, an armature biased away from said electro-magnet to a first position, energization of said electro-magnet being effective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position for operation of a circuit breaker automatic tripping means, said member being mounted for movement away from said tripping position to a latching position, means for engaging said member and maintaining same in said latching position, said means being operatively connected to said armature for operation in accordance with movement of said armature, a pivot pin, said armature mounted on said pivot pin, means defining a stationary elongated slot means wherein said pivot pin is confined, a spring connected between a stationary member and said armature biasing the latter away from said magnet about said pivot pin as a pivot point, the pivotal mounting of said armature effective to prevent over-latching and overtravel, with said spring acting as a cushion.

5. A circuit breaker comprising a pair of cooperating contacts, a movable arm carrying one of said contacts, a mechanism connected to said arm for operating said contacts into and out of engagement, a trip device which when operated permits automatic disengagement of said contacts; an auxiliary trip unit comprising an electro-magnet, an armature, including an extending portion, biased away from said electro-magnet to a first position, energization of said electro-magnet being etfective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position wherein said member operates said trip device, said member being operated away from said tripping position to a latching position during disengagement of said contacts by an extension thereof engageable with means mounted to said movable arm, means for engaging said member and maintaining same in said latching position, said latching means being carried by said extending portion of said armature for operation in accordance with movement of said armature.

6. A circuit breaker comprising a pair of cooperating contacts, a movable arm carrying one of said contacts, a mechanism connected to said arm for operating said contacts into and out of engagement, a trip device which When operated permits automatic disengagement of said contacts; an auxiliary trip unit comprising an electromagnet, an armature biased away from said electro-magnet to a first position, energization of said electromagnet being effective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position wherein said member operates said trip device, said member being operated away from said tripping position to a latching position during disengagement of said contacts by an extension thereof engageable With means mounted to said movable arm, means for engaging said member and maintaining same in said latching position, said latching means being operatively connected to said armature for operation in accordance with movement of said armature, a pivotal mounting means for said armature comprising a pivot pin and means defining an elongated slot means wherein said pivot pin is confined, spring means biasing said armature away from said magnet about said pivot pin as a pivot point, the pivotal mounting of said armature effective to prevent over-latching and overtravel, with said spring acting as a cushion.

7. An auxiliary trip unit for a circuit breaker, said unit comprising an electro-magnet, an armature biased away from said electro-magnet to a first position, energization of said electro-magnet being effective to operate said armature toward said electro-magnet to a second position, a latch member biased to a tripping position for operation of a circuit breaker automatic tripping means, said member being mounted for movement away from said tripping position to a latching position, latch means for engaging said member and maintaining same in said latching position, said latch means being operatively connected to said armature for operation in accordance with movement of said armature, a pivotal mounting for said armature comprising a pivot pin and means defining an elongated slot References Cited in the file of this patent UNITED STATES PATENTS 1,292,651 Rippl Jan. 28, 1919 1,336,764 Thomson Apr. 13, 1920 2,912,544 Piteo et al Nov. 10, 1959 2,938,980 Jencks May 31, 1960 

1. A AUXILIARY TRIP UNIT FOR A CIRCUIT BREAKER, SAID UNIT COMPRISING AN ELECTRO-MAGNET, AN ARMATURE, INCLUDING AN EXTENDING PORTION, BIASED AWAY FROM SAID ELECTRO-MAGNET TO A FIRST POSITION, ENERGIZATION OF SAID ELECTRO-MAGNET BEING EFFECTIVE TO OPERATE SAID ARMATURE TOWARD SAID ELECTRO-MAGNET TO A SECOND POSITION, A LATCH MEMBER BIASED TO A TRIPPING POSITION FOR OPERATION OF A CIRCUIT BREAKER AUTOMATIC TRIPPING MEANS, SAID MEMBER BEING MOUNTED FOR MOVEMENT AWAY FROM SAID TRIPPING POSITION TO A LATCHING POSITION, MEANS FOR ENGAGING SAID MEMBER AND MAINTAINING SAME IN SAID LATCHING POSITION, SAID MEANS BEING CARRIED BY SAID EXTENDING PORTION OF SAID ARMATURE FOR OPERATION IN ACCORDANCE WITH MOVEMENT OF SAID ARMATURE. 